Furnace



y 1,624,043 April l2 1927' F. A. FAHRENWALD FURNACE Filed Jan, 13. 1926 3 Sheets-Sheet'l IA///l/ MRL [zzz/enfer l] M/MM .Attorneys April 12,1927. 1,624,043

F. A.k FAHRENWALD FURNACE Filed Jan. l5.y 1926 3 Sheets-Sheet 2 frank. A.. Pahrenwald. [nvezzor Attorneys 1,624,043 APIll 12 1927' F, A. FAHRENWALD FURNACE Filed Jan. 15. 1926 3 Sheets-Sheet 3 4 frani-Aahrezzwzd Ml-m Patented Apr..r l2, 19527. l

STES PAT.

E A. FAHBEE'WALD, 0F CHICAGO, XLLINOIS.

FURNACE.

Application lc. January 13, 1926. Serial No. 80,960.

This invention rela-tes to furnaces and has have heretofore been madelto employ instead special reference to those furnaces, someof cast iron a suitable alloy more resistant times denominated process furnacesl which to high temperatures, but this change alone are u'ied for metallurgical and chemical opoil'ers no suihcient advantages over elast4 iron 60 erations. The objects of the invention are !o warrant the increased expense, since the provision of new, improved and simpli breakage of the arms by dislodged bricks fied mechanism for stirring, scraping and or by the failure of other arms would still` advancing the substance being treated, occur as before and with no increased fawhereby the initial cost is reduced, the life is cility of replacement. l have devised, howl" increased, injury consequent upon breakage ever, a mode of mounting such an arm as to is minimized, and replacement facilitated. avoid these difficulties of breakage and re- For 'example Some of hesefurnaces as placement, thereby rendering feasible the employed for the roasting of ore are as much use of the more expensive materials. Briefly as twenty feet in diameter and forty feet stated this invention consists in pivoting the l high with a five foot vertical shaft in the arm to the operating shaft upon a hinged cen/ter provided with radial arms which yjoint, and normally holding the same in opoverliang circular hearths carried one above erating position by a frangilole member the olier bythe furnace wall. Thesehearths adapted to yield upon an excessive stress. are provided with discharge openings lofurther refinement of the invention con- 3" cated alternately near the center and lnear slstsin mounting the hinge pivot at such an the periphery and the lower edge of each angle relative to the shaft that as the arm arm is provided with a plurality of suitable is released and swings away from its operatplows or stirring blades adapted to turn the ing position 1t is also drawn away from the material, keep it stirred, and slowly move surface of the hearth to ywhich it is nearest, it inwardly or outwardly aS the case may thereby reducing the danger of wedging or be, a current of flame or of oxidizing gases breakage. A preferred embodiment comprebeing meanwhile produced over these bending these and other features of my inhearths so as to maintain the whole at a tem- Vention is shown in the drawings accomperature of from 1000 to 1850F. This p anying and forming a art of this applica 85 l shaft has heretofore ordinarily been cooled tion, although it will e understood that by water or air and the arms also have conthese are intended to be 'merely illustrative tained extension conduits for the cooling of the general principles of my invention -and fluid.v Owing to the warping of the arms, are not exhaustive of the detailed constructhe development of aws, or the loosening tions possible tovbe'ernployed. of bricks under the influence of the high Fig. lis a vertical sectional view illustrartemperature, it is not an uncommon occurlng in somewhat simplified form the main rence for an arm to become wedged and features of such a furnace; Fig. 2 is a horibroken off 'and the breakage of one arm is zontal sectional view corresponding to the generally followed by the breakage of all line 2.2 of Fig.l 1; Fig. 3 is a perspective other arms carried by the center shaft at the View of the inner hinged end of one of the same level. 'lfhese arms are generally rigrabble arms showing same in working posiidly bolted to the center shaft in some inantion; Fig. fi is a perspective view of the same ner so as to he capable of replacement, but members after the failure of the frangible owing to the high temperature of the parts, member; Fig. 5 is a vertical sectional view 'the replacements of such an arm requires of one of the arm supporting members' Fig. anywhere from a few hours to 'several days, (i isa horizontal sectional View through a during which time the entire furnace is out modlfied form of shaft equipped with my of. commission, and in addition the breakage invention; Fig. 7 is a side eievation of an u of a water-cooled arm inside a hot furnace alternative 'type of rabble arm secured to a 1T is likely to be attended with extreme unsectional form of shaft; and Fig. 8 is a. top

pieasantness or danger. lan view of the arm shown in Fig. Y.

The materiai heretofore ordinariiy em-v The furnace generally comprises an npployed for these arms has 4been cast iron, the right cylindrical body l, aitheugh the same cooiing iiciuid being trusted 'to maintain its may be horizontal or inclined. lin the presit@ temperature suiii'cientiy towto keep it within ent embodiment this body is its established strength limits. la

gestions ferent vertieai heights with ci? zontal vshelves or ledges 2-2 constituting hearths extending close to the wall and having circular apertures 3 at ,the center, and between these with other circular horizontal ledges 4 1 having holes 5 near the furnace outer wall and also having central holes 6 in line with the openings 3. i

Vertically extending through the holes 3 and 6 is the upright shaft 7 provided at one end, generally the bottom, with a suitable rotating device as the bevel gear 8 meshing with the driving gear 9, and secured to thls shaft above each one of the shelves are one or two or more horizontal arms 10-10 known as rabble arms, their lowe'r edges provided with suitable Scrapers or blades 11 and 12 respectivel The blades 11 which sweep over the she ves 2 2 are so arranged as to plow the material towards the center while the blades 12 which sweep over the shelves 4 are arranged to plow the material away from the center towards the discharge openings 5. Raw material, such as ore to be roasted or converted, is fed gradually to the top of the furnace by suitable means such as the spout 55, and heat may, if dei' sired, be supplied to the lower end of the furnace by a suitable furnace indicated at 57 although in the case of sulphurous ores it sometimes occurs that the oxidation of the sulphur provides sufficient heat for the purpose. In any case the furnace wall is provided above each ledge or shelf with closable openings-- of sufficient size to permit the entrance of a man or to enable the replacement of parts therethrough.

rIhe shaft 7 may be made of any desired material which i's sulicient to stand the mechanical strain at the working temperature. Heretofore the usual practice has been either, as exem lilied in the so-called Wedge furnaces and KfcDougall furnaces, respectively, to make the shafts of steel or cast iron, shielded either by an external covering of bricks, or internally by circulating fluid. The shaft shown in Figs. 1 and 2 hereof is specifically the Wedge type which comprises a cylindrical metal shell 15 surrounded by bricks as shown at 16 and formed with radial apertures for the reception of the base portions 17 of the rabble arms. Each of these base ends ordinarily comprises a cylindrical member 18 adapted to enter a hole in the shaft and a tapering portion 19 adapted to 'tit a suitable seat and be securedthereto by any suitable means (not shown). The inner diameter of this shell 15 is ordinarily several feet and in it are located vertical conduits 20-20 for cooling iuid, water or air, suitable connections 21 extending thence to the arm bases which are made hollow and provided with a central partition 22 in order to direct the current.

In order to apply my improvements `to a furnace of tais nature I make a base pornaaeofia tion of size and shape to fit the standard openings in the shaft, but instead 'of making this portion integral with the arm as in the Wedge furnace, and carrying the fluid circulation ducts clear to the end thereof, I terminate this base portion close to the liange 19 by an imperforate end wall 23 beyond which project at one side the two vertically spaced ears 24-24 apertured for the reception of the hinge pin 25. The arm 10 ,is made of any desirable section to combine strength with lightness, preferably the well known I-beam with vertical web and flanges at top and bottom. At its base this arm is provided with ears 26-26 matching the ears 24 and similarly apertured for the same pin. In order to hold this arm radial during practical operation of the-:furnace I provide a suitable frangible member of suitable strength to carry all normal and proper operating loads but so vlimited in strength as to break before any` strain is reached which endangers the other parts. Preferably this member consists of a bolt 27 of suitable metallic composition laid in vtthe notches 28-28 of two ears 29-29 which project, one from the base portion and the other `from the side of the arm, the same being sufficiently removed from tbe hinge pin to separate along a predetermined are. This bolt is provided at one end with a head 30 and at the other end with a nut or collar 31 which cooperates with the ears to hold the arm against movement. This arrangement, while not indispensable, is highly convenient practicallyfor numerous reasons. In the first place a frangible member operating at high temperature is better ruptured by a pull than by a bend or shear both because such rupture occurs at a more definite and predictable point, and because after rupture it leaves the parts in better condition for replacement. Upon rupture of this bolt for any reason the arm merely swings laterally to the dotted position shown in F ig. 2. rlhe notches 28-28 are easily brought into line with one of the openings 56 by rotating the shaft slowly and whenever this occurs it is easy to apply a new tension bolt by inserting the projecting end thereof into one end of a piece of pipe which is then thrust into the furnace until the bolt drops into its place and the pipe is withdrawn.

Another type of furnace mentioned is the McDougall, a cross section of the shaft being shown in Fig. 6. This shaft consists of a massive column 35, generally of cast iron, having opposed flattened portions 36-36 to which the arms are detachably secured. rlhe interior of the shaft is cooled by moving air or water and ordinarily suitable conduits forcooling li uid are carried-out into the arms. 'llo app y my improvements to a furnace of this type, I provide a plate member 37 formed at one side with ears 33 Cil mamas -apertured for the hinge pin 39 and at the a very great waste of heat but also, vin casewater is employed, as usually has to be done when common steel and cast iron are the materials employed, greatly increases the danger of property damage and loss of life in the event of any breakage. In order. to obtain the full benefits-of my invention it is best to employ a shaft also made of a high temperature alloy and one form which such a shaft may take is illustrated in Figs. 7 and 8 wherein 45 represents a single length of such shaft formed at its upper and lower ends with flanges 46-46 for the attachment of adjacent sections. In this case the ears 48-48 are preferably cast directly on the section as are also the slotted ears, 49, which receive the frangible bolts 50. Owing to the fact that no heed need now be paid to rcplacement diiculties', it becomes possible to simplify the design, locating the companion ears 51 beyond the end of the arm and in line therewith. I have here shown a bolt 50 of greater length. i

Inrall these cases, however, the hinge bolts are `preferably located with their axes making a slight oblique angle with the axis of the shaft so that the lateral swinging of the arm shall not only bring it nearer the periphery of the shaft but shall also tend to lift it gradually away from the hearth and thus decrease the danger of catching anything to `produce further breakage. It will be obvious that this effect could be produced either by leanin the ins directly awa from the shaftor y leanlngthem lat eral y of the shaft, and I prefer the latter arrangement sinne it produces a more immediate lifting of the arm. In either case it will be understood that thisis a refinement of the eneral idea.

It will be understood that the improvements here described can be employed onl if the parts are made of some alloy which will maintain the necessary mechanical strength at the Working temperatures. Various alloys have been marketed within the,`

last few years which will serve this requirement and that which I prefer consists of alloys of chromium and iron group metals, preferably with a little silicon and substantially without carbon. A very satisfactory alloy is made of 17% chromium, 2% silicon, 33% nickel and the balance iron, but I do not limit myself to any particular type of composition of alloy. It is only necessary to employI some type of arm which will withstand the Working temperatures without the i necessity of cooling fluid, although 'merely to make the old type of arm of such high temperature material offers'no substantial improvement from the practical aspect unless further the prevention of accidental breakage such as I have here done. In case of the use of special alloy shafting as shown in Figs. 7 and 8 it is generally best to blow air through the same to moderate its temperature, but

water with its inconvenience and dangers can be ehmmated.

It will be understood that many changes in detail can be made vwithout departing fromthe scope of my invention, and all such changes it is my purpose to claim and secure excepting only a's my claims are lrestricted by the prior art.

Having thus claim:

l. In a process furnace, the combination with rabble arms of a driving member to whichsaid arms are attached, such attachment including pivoting provisions and a frangble element normally securing the parts against pivoting movement but adapted to yield upon excessive stress.

2. In a process furnace, the combination with a material-supporting hearth and a driving member movable relativel thereto, of a rabble arm attached to saidy member, ploughing blades carried 'by said armin a posltlon to sweep over said hearth, the attachment betweensaid arm and member in cluding a hinge joint, and means including a frangible element for holding said hingejoint rigid, said element adapted to yield upon excessive stress and permit hinging prior to breaking said arm.

3. In a process furnace, the combination with a material-supporting hearth and a driving member movable relatively thereto,

described my invention, I

provision be made for of a yrabble arm attached to said member,

position to sweep over saidV hearth, the attachment between said arm and member inf cluding a hinge joint, and means lincluding a frangible element for holding said hingejoint rigid, said hin e joint bein so arranged that after brea ing of said ranvible element the arm is free to move away rom saidv hearth. l

4. In a process furnace the combination with an upright hollow body having annular shelves therein constituting hearths and an upright shaft concentric with said hearths, of rabble arms connected to said shaft and projecting over said hearths, such connections including hnge-joints whose axes are approximately lengthwise of said shaft, and a frangible member associated with each of said joints adapted t0 hold the arms rigid until a predetermined breaking stness is imposed thereon.

5. ln a process furnace the combination with an upright hollen7 body having annular shelves therein` constituting hearths and an upright shaft concentric with said heartbs, of rabble arms connected to said shaft and projecting over said hearths, such connections including hinge-joints whose axes are oblique both to the shaft and to the planes of said hearths.

6. In a process furnace the combination with an upright shaftI and a circular hearth, of rabble arms connected to said .shaft and projecting over said hearth, such connection including a frangible element adapted to yield upon excessive strain and permit the arm to move out of operating position, and also including a non-rigid device which supports said arm. after the breaking of said frangible element,

'4'. ln a process furnace, a rabble arm baving a. hinge joint therein, in combination with means foi-holding said joint rigid, said nleans including a frangible member de signed to yield under predetermined stress.

8. ln a process furnace, a shell having openings, a rotatable shaft inside said shell, rabble arms connected to said shaft, such connections including hinge joints, and means for holding said hinge joints rigid, said means including frangible members Lessinia adapted to yield upon a given stress and saidv members being accessible and replaceable from the exterior of said shell by way of said openings.

9. In a process furnace, a shell and a rotatable shaft therein, rabble arms connected to said shaft, such connections including hinge joints adapted and arranged to permit said arms to swing transversely of the shaft, and also including franglble members adapted tol prevent hinging movement, said members, beng located approximately perpendicular to the hinge axes.

10. ln a process furnace, a rabble arm, a driving shaft therefor, and connections between said arm and shaft including a hinge joint and a frangible member, said hinge joint adapted to support the Wei ht of said arm and said member to hold t e same in operating position.

11. ln a process furnace, a rabble arm, a driving shaft therefor, connections between said shaft and arm for supporting the Weight of said arm, and other connections for holding the same in operating position, the supporting connection comprising a nonrigid member and the other connection coinprising a frangible member.

ln testimony whereof l hereunto ellis. my signature.

FRANK A. FAHRENl/VALD. 

